Integrated tab bar UI elements (#7853)

## Summary

The current help / feedback is often overlooked by users, this adds a
setting that makes it more visible moving it up into the tab bar and
moves the user login/profile button out of the "action bar" into the tab
bar.

## Changes
- Add 'Comfy.UI.TabBarLayout' setting with Default/Integrated options
- Move Help & User controls to tab bar when Integrated mode is enabled
- Extract help center logic into shared useHelpCenter composable

## Screenshots (if applicable)

<img width="515" height="540" alt="image"
src="https://github.com/user-attachments/assets/c9e6057f-4fb1-4da6-b25d-9df4b19be31a"
/>
<img width="835" height="268" alt="image"
src="https://github.com/user-attachments/assets/24afc0e8-97eb-45cf-af86-15a9b464e9a8"
/>

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7853-Integrated-tab-bar-UI-elements-2df6d73d365081b1beb8f7c641c2fa43)
by [Unito](https://www.unito.io)

---------

Co-authored-by: GitHub Action <action@github.com>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

src/platform/settings/constants/coreSettings.ts

@@ -549,6 +549,16 @@ export const CORE_SETTINGS: SettingParams[] = [
       }
     }
   },
+  {
+    id: 'Comfy.UI.TabBarLayout',
+    category: ['Appearance', 'General'],
+    name: 'Tab Bar Layout',
+    type: 'combo',
+    options: ['Default', 'Integrated'],
+    tooltip:
+      'Controls the layout of the tab bar. "Integrated" moves Help and User controls into the tab bar area.',
+    defaultValue: 'Default'
+  },
   {
     id: 'Comfy.UseNewMenu',
     category: ['Comfy', 'Menu', 'UseNewMenu'],